A blue frontplate to a circuit board is shown. On the left side is an OLED screen displaying "4.35 µH". To the right of this are a red and a black socket, with an inductor between them.

Building An LC Meter With A Franklin Oscillator

March 18, 2026 by No comments

Although it dates back to the early days of the Marconi Company in the 1920s, the Franklin oscillator has remained a relatively obscure circuit, its memory mostly kept alive by ham radio operators who prize its high stability at higher frequencies. At the core of the circuit is an LC tank circuit, a fact which [nobcha] used to build quite a precise LC meter.

The meter is built around two parts: the Franklin oscillator, which resonates at a frequency defined by its inductance and capacitance, and an Arduino which counts the frequency of the signal. In operation, the Arduino measures the frequency of the original LC circuit, then measures again after another element (capacitor or inductor) has been added to the circuit. By measuring how much the resonant frequency changes, it’s possible to determine the value of the new element.

Before operation, the meter must be calibrated with a known reference capacitor to determine the values of the base LC circuit. In one iteration of the design, this was done automatically using a relay, while in a later version a manual switch connects the reference capacitor. Because the meter measures frequency differences and not absolute values, it minimizes parasitic effects. In testing, it was capable of measuring inductances as low as 0.1 µH.

We’ve seen a few homebrew LC meters here, some battery-powered and some rather professional.

Testing Whether Heated Chambers Help Brittle Filaments

March 17, 2026 by No comments

Some FDM filaments are pretty brittle even if properly dried and stored, especially those which contain carbon fiber (CF) or similar additives like glass fiber (GF). This poses a problem in that these filaments can snap even within the PTFE tube as they’re being guided towards the extruder. Here a community theory is that having an actively heated chamber can help prevent this scenario, but is it actually true? [Dr. Igor Gaspar] of the My Tech Fun YouTube channel gave this myth a try to either confirm or bust it.

The comments suggested that heating the chamber to 65°C will help, but there’s little information online to support this theorem. To test the claim, a heated chamber was used along with a bending rig to see at which angle the filament would snap. In total five different filaments from three manufacturers (Polymaker, Qidi and YXPolyer) were tested, including Qidi’s PET-GF and PAHT-GF as the sole non-CF filaments.

A big question is how long exactly the filament will spend inside the heated chamber after making its way from the spool, which would be about 2.5 minutes with a 500 mm tube. For the test 5 minutes was used for the best possible result. Despite this, the results show that even with the standard deviation kept in mind, the heating actually seems to make the filaments even more brittle.

Considering that in general CF seems to simply weaken the polymer matrix after printing, this finding adds to the question of whether these CF and GF-infused filaments make any sense at all.

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How To Grow Large Sugar Crystals

March 17, 2026 by 4 Comments

Many substances display crystallization, allowing them to keep adding to a basic shape to reach pretty humongous proportions. Although we usually tend to think of pretty stones that get fashioned into jewelry or put up for display, sugar also crystallizes and thus you can create pretty large sugar crystals. How to do this is demonstrated by [Chase] of Crystalverse fame in a recent video.

This is effectively a follow-up to a 2022 blog article in which [Chase] showed a few ways to create pretty table sugar (sucrose) based crystals. In that article the growth of single sucrose crystals was attempted, but a few additional crystals got stuck to the main crystal so that it technically wasn’t a single crystal any more.

With this new method coarse sugar is used both for seed crystals as well as for creating the syrupy liquid from mixing 100 mL of water with 225 grams of sugar. Starting a single crystal is attempted by using thin fishing wire in a small vessel with the syrup and some seed crystals, hoping that a crystal will lodge to said fishing wire.

After a few attempts this works and from there the crystals can be suspended in the large jar with syrup to let them continue growing. It’s important to cover the jar during this period, as more crystals will form in the syrup over time, requiring occasional removal of these stray ones.

Naturally this process takes a while, with a solid week required to get a sizeable crystal as in the video. After this the crystal is effectively just a very large version of the sugar crystals in that 1 kg bag from the supermarket, ergo it will dissolve again just as easily. If you want a more durable crystal that’s equally easy to grow, you can toss some vinegar and scrap copper together to create very pretty, albeit toxic, copper(II) acetate crystals.

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Zip-Drive Emulator Puts Big Disks Back On LPT

March 17, 2026 by 11 Comments

Iomega’s Zip drives filled an interesting niche back in the 1990s. A magnetic disk that was physically floppy-sized, but much larger in capacity– starting at 100 MB, and reaching 750 MB by the end–they never quite had universal appeal, but never really went away until flash memory chased them out of the marketplace in the early 2000s. While not everyone is going to miss them, some of us still think it’s a better form factor than having a USB stick awkwardly protruding from a computer, or microSD cards that are barely large enough to see with the naked eye. [Minh Danh] is one of those who still has affection for Zip drives, and when his parallel port Zip 100 drive started to give up the ghost last year, he decided to do something bold: reverse engineer it, and produce an emulator. First software, and then in hardware.

It’s not the prettiest-ever prototype, but lots of great things start with a mess of wires.

The first was to create a virtual zip drive that could run on a virtual machine and be accessed with DOS or Windows up to XP. The next task was to move that functionality onto a microcontroller to create something like a GoTek floppy emulator for LPT Zip drives that he’s calling the LPT100. Yes, Zip drives were built for APATI, SCSI, FireWire and USB, too, but [Minh]’s was on the parallel port and that’s what he wanted to replace, so the LPT interface is what set out to recreate.

It works, too, though took more guts than was expected– the 8-bit PIC18F4680 he started with just wasn’t up to the task. He moved up to a 32-bit PIC, the PIC32MZ2048EFH144 to be specific, which proved adaquate when testing with his Book 8088, a new DOS PC from 2023. Iomega’s official driver won’t run on an 8088, but the PALMZIP utility does and was able to transfer files, though only at the slow nibble rate due to limitations with the Book8088’s LPT hardware. Watch it in action below.

Alas, moving up to the Pocket386, it seemed the PIC just could not keep up. [Minh] says he’s thinking of moving to the faster Teensy 4.1, which sounds like a good idea. Considering the Teensy can be configured to serve as a drop-in replacement for a 68000, bit-banging the bus at 7.8 MHz, we’d think it should handle anything a parallel port can throw at it.

Thanks to [Minh Danh] for the tip!

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Testing A Soviet 1000 Volt Insulation Tester From 1985

March 17, 2026 by 4 Comments

Although the term ‘Iron Curtain’ from the Cold War brings to mind something like the Berlin Wall and its forbidding No Man’s Land, there was still active trade between the Soviet Union and the West. This included devices like the M4100/4 insulation tester that the [Three-phase] YouTube channel recently looked at, after previously poking at a 1967 USSR resistance bridge.

This particular unit dates to 1985, and comes in a rather nice-looking case that somewhat looks like bakelite. It’s rated for up to 1 gigaohm, putting out 1,000 V by using the crank handle. Because of the pristine condition of the entire unit, including seals, it was decided to not look at the internals but only test its functionality.

After running through the basic usage of the insulation tester it’s hooked up to a range of testing devices, which shows that it seems to be mostly still in working condition. The first issue noticed was that the crank handle-based generator was a bit tired, so that it never quite hit the maximum voltage.

With no parallax correction and no known last calibration date, it still measured to about 10% of the actual value in some tests initially, but in later tests it was significantly off from the expected value. At this point the device was suspected of being faulty, but it defied being easily opened, so any repair will have to be put off for now. That said, it being in such good condition raises the prospect of it being an easy repair, hopefully in an upcoming video.

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Preparing To Fire Up A 90-Year-Old Boiler After Half A Century

March 17, 2026 by 2 Comments

Continuing the restoration of the #1 Lancashire boiler at the Claymills Pumping Station in the UK, the volunteers are putting on the final touches after previously passing the boiler inspection. Although it may seem that things are basically ready to start laying down a fire after the boiler is proven to hold 120 PSI with all safeties fully operating, they first had to reassemble the surrounding brickwork, free up a seized damper shaft and give a lot of TLC to mechanisms that were brand new in the 1930s and last operated in 1971.

Removing the ashes from a Lancashire boiler. (Credit: Claymills pumping station, YouTube)
Removing the ashes from a Lancashire boiler. (Credit: Claymills pumping station, YouTube)

The damper shaft is part of the damper mechanism which controls doors that affect the burn rate, acting as a kind of throttle for the boilers. Unfortunately the shaft’s bearings had seized up completely, and no amount of heat and kinetic maintenance could loosen it up again. This forced them to pull it out and manufacture a replacement, but did provide a good look at how it’s put together. The original dial indicator was salvaged, along with some other bits that were still good.

Next was to fit the cast-iron ash boxes that sit below the boiler and from where ash can be scraped out and deposited into wheelbarrows. The automatic sprinkler stokers are fitted above these, with a good look at their mechanism. The operator is given a lot of control over how much coal is being fed into the boiler, as part of the early 20th-century automation.

The missing furnace doors on the #1 boiler were replaced with replicas based on the ones from the other boilers, and some piping around the boiler was refurbished. Even after all that work, it’ll still take a few weeks and a lot more work to fully reassemble the boiler, showing just how complex these systems are. With some luck it’ll fire right back up after fifty years of slumbering and decades of suffering the elements.

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Hacking The System In A Moral Panic: We Need To Talk

March 17, 2026 by 37 Comments

It seems that for as long as there have been readily available 3D printers, there have been moral panics about their being used to print firearms. The latest surrounds a Washington State Legislature bill, HB2320, which criminalises the printing of unregistered guns. Perhaps most controversially, it seeks so impose a requirement on printers sold in the state to phone home and check a database of known firearms and refuse to print them when asked.

This has drawn a wave of protest from the 3D printing community, and seems from where we are sitting to be a spectacularly ill-conceived piece of legislation. It’s simply not clear how it could be implemented, given the way 3D printers and slicing software actually work.

Oddly This Isn’t About Firearms

The root of the problem with this bill and others like it lies in ignorance, and a misplaced belief in the power of legislation. Firearms are just the example here, but we can think of others and we’re sure you can too. Legislators aren’t stupid, but by and large they don’t come from technology or engineering backgrounds.

Meanwhile they have voters to keep happy, and therefore when a moral panic like this one arises their priority is to be seen to be doing something about it. They dream up a technically infeasible solution, push to get it written into law, and their job is done. Let the engineers figure out how to make it work. Continue reading “Hacking The System In A Moral Panic: We Need To Talk” →